OBJECTIVE To determine the prevalence of psychiatric disorders, especially depressive illness, in elderly medical inpatients. METHODS University Hospital Leiden. METHODS Two-stage design. METHODS In six somatic wards a series of 250 patients were randomly selected and screened with two self-rating scales for depression (Beck Depression Inventory, Geriatric Depression Scale) and one screening scale for cognitive dysfunctions (Mini-Mental State Examination). The 52 drop-outs differed significantly from the other patients only in a greater general illness severity, and a higher prevalence of a psychiatric history. Eighty-two patients were selected for a diagnostic procedure with a standardised, semi-structured psychiatric interview, and were classified according to the DSM III-R. Fifty-nine of them were probable cases according to the screening instruments, 23 were selected at random from the probable non-cases. RESULTS A psychiatric disorder was detected in 25 patients, all but one patient with schizophrenia were found in the group of probable cases. Only five patients were classified as major depression, which lead to a prevalence rate of 2.9% (95% CI 0.4-5.4%). We found evidence of many psychiatric disorders in the group of 52 drop-outs, but these were mostly organic psychiatric disorders, and just one mood disorder. CONCLUSIONS The prevalence of major depression is lower than found until now among elderly medical inpatients.